The proposed research examines cross-sectional and longitudinal relationships of depression and conduct problems to use of marijuana, cigarettes, and alcohol in an understudied population, African-American adolescents. Data from this project are drawn from two unique studies: Monitoring the Future (MTF), a large, national study of substance use and related constructs and SCHOO-BE, a laboratory study of substance use and mental health in a large sample of urban African American adolescents. This project maximizes the respective advantages of survey and laboratory research by exploring longitudinal relationships of substance use and mental health and their potential common underlying mechanisms, with two aims. First, this research aims to examine the cross-sectional relationships between depression, conduct problems, and marijuana, cigarette, and alcohol use in two African American adolescent samples: SCHOO-BE and a demographically comparable sample selected from MTF. Second, this research aims to further characterize the relationships of mental health symptoms to substance use, capitalizing on strengths of each dataset by conducting longitudinal analysis in MTF of depression and conduct problems predicting future marijuana, cigarette, and alcohol use, and by testing a mediation model in SCHOO-BE in which conduct problems and depression mediate the relationship between parental support and marijuana, cigarette, and alcohol use. The current project will contribute important knowledge on the developmental trajectories of substance use in African-American adolescents. This population is underrepresented in the extant literature, and results of studies of non-African-American samples cannot be assumed to generalize to them. Research to date has revealed that African-Americans are more likely to experience substance-related problems such as substance use disorder and negative health consequences despite lower rates of use during adolescence. However, the role of mental health, specifically depression and conduct problems, in African-Americans' marijuana, cigarette, and alcohol use and their progression to problematic use has not yet been elaborated. The findings yielded by the proposed research will have immediate relevance for culturally specific prevention and intervention programs to reduce substance use by African-American youth by targeting mental health symptoms. The research training component of the project is centered on three training goals for the Principal Investigator, Julie Maslowsky: to increase grant and manuscript writing skills, expand empirical skills, and further develop her multidisciplinary professional network. The training will be accomplished over two years via a rigorous program of courses and workshops that teach the skills Julie wishes to learn, individual and lab meetings where she receives guidance on her research progress and her professional development, collaboration with colleagues from multiple disciplines, and presentations at the major multidisciplinary conferences in the field. Receipt of this training will prepare her well for her intended career as an independent developmental science researcher.